The present invention relates generally to the field of devices and techniques for rapidly raising the temperature of semiconductor samples and, more particularly, to apparatus and techniques for transient annealing of ion-implanted semiconductor samples.
The technique of ion implantation has, over the last ten years, gained wide acceptance as a means whereby the electrical conductivity of semiconductor samples may be selectively modified and controlled in a reproducible and predictable manner. This technique, in particular, has been shown to be appropriate for the fabrication of LSI chips and the processing of large wafers because of its extreme uniformity and its adaptablity to a planar technology via selective implantation of both n-type and p-type as well as deep compensating species via photoresist, oxide, or metal masks. It is well known that essential to this technique, however, is a means whereby, following implantation, the ion species may be made electrically active and lattice damage resulting from the implant may be removed. This is most usually accomplished via annealing wherein the sample is raised in temperature for about ten to fifteen minutes during which time the structural rearrangement of the sample surface region is allowed to take place. Because of the significant temperatures involved (e.g. typically 950.degree. C. for Si, 850.degree. C. for GaAs, and 700.degree. C. for InP) this part of the process has often been a source of difficulty, including the observation of impurity and dopant redistributions due presumably to diffusion and damage gettering and thermal degradation of the surface sample, particularly for the compounds with their highly volatile constituents. In the past, these annealing techniques have usually been accomplished by means of a furnace where a fifteen minute anneal would typically be used.
To help alleviate these problems as well as decrease processing times, transient, short time or "flash" annealing methods have recently been reported wherein the sample is rapidly heated and maintained at an elevated temperature for times no greater than thirty seconds or so. Typically, pulsed or scanned electron beams, laser beams, or high intensity lamps are used to generate the thermal transients with varying degrees of success being reported for both Si as well as compound semiconductors. All of these recently reported systems operate far from thermal equilibruim making accurate measurement of sample temperature difficult.